1. Field of the Invention
The present invention relates to a radio-frequency (RF) front-end module that transmits and receives, with a common antenna, a plurality of communication signals in different communication frequency bands.
2. Description of the Related Art
Various conventional RF front-end modules that transmit and receive a plurality of communication signals in different communication frequency bands have been put to practical use. Among these modules, there are RF front-end modules that transmit and receive communication signals with a common antenna for the communication signals.
When such a common antenna is used, generally transmitting and receiving circuits for the individual types of communication signals are switched and connected to the common antenna. Further, as illustrated in Japanese Unexamined Patent Application Publication No. 2010-045563, the transmitting circuit and the receiving circuit for each type of communication signal are connected to a switch element via a duplexer including a filter that passes a transmission frequency and a filter that passes a reception frequency.
In the Wideband Code Division Multiple Access (W-CDMA) communication system defined at present, the reception frequency band of communication signals in Band 1 ranges from about 2110 MHz to about 2170 MHz, and the reception frequency band of communication signals in Band 4 ranges from about 2110 MHz to about 2155 MHz. Therefore, the reception frequency band of communication signals in Band 1 and the reception frequency band of communication signals in Band 4 partially overlap.
In such a case, an RF front-end module such as that illustrated in FIG. 1 has been used. FIG. 1 is a circuit diagram of an RF front-end module 10P of the related art. The RF front-end module 10P includes power amplifiers 11 and 12, duplexers 21 and 22, and a switch integrated circuit (IC) 30P.
A transmission signal of a first communication signal (first transmission signal) input from a first transmission signal input terminal Ptx1 is output to a first common terminal Pc1 via the power amplifier 11 and a transmission-side filter 211 of the duplexer 21.
A transmission signal of a second communication signal (second transmission signal) input from a second transmission signal input terminal Ptx2 is output to a second common terminal Pc2 via the power amplifier 12 and a transmission-side filter 221 of the duplexer 22. The first transmission signal output from the first common terminal Pc1 and the second transmission signal output from the second common terminal Pc2 are transmitted from a common antenna (not illustrated) to the outside via a switch element (not illustrated).
A reception signal of the first communication signal (first reception signal) input via the common antenna and the switch element (both are not illustrated) to the first common terminal Pc1 is output to the switch IC 30P via a reception-side filter 212 of the duplexer 21.
A reception signal of the second communication signal (second reception signal) input via the common antenna and the switch element (both are not illustrated) to the second common terminal Pc2 is output to the switch IC 30P via a reception-side filter 222 of the duplexer 22.
The switch IC 30P outputs the first reception signal to a reception signal output terminal Prx12 at the time of reception control of the first reception signal, and outputs the second reception signal to the reception signal output terminal Prx12 at the time of reception control of the second reception signal.
The RF front-end module 10P such as that illustrated in FIG. 1 has large circuit dimensions since the RF front-end module 10P has a duplexer for each type of communication signal. In order to comply with the specification of a reception signal modulator circuit and the like, which is provided for reception signals subsequent to the RF front-end module 10P, reception signals are normally output as balanced signals, and the switch IC 30P of the related art is a double-pole four-through (DP4T) switch. This point also increases the circuit dimensions. Therefore, it is difficult to miniaturize the RF front-end module 10P of the related art.